The present invention relates to the pitch actuating and control of helicopter blades, and more particularly, to the independent adjustment of both collective and cyclic pitches by direct action on the blade hubs only.
Since helicopters were developed and almost universally, the setting and control of the angle of attack (pitch) of helicopter blades have been performed, for both collective and cyclic pitches, by means of a swash plate that moves up and down and can also tilt. These two independent types of motion provide the means to set and control the blade pitch for any power setting and/or direction of motion of the helicopter. The swash plate is linked to the edge of the blade, near the blade hub attachment to the vertical main power drive shaft. This means that the swah plate and the linkage arrangement are usually not enclosed and are exposed to any environmental conditions that may prevail around the helicopter (sand, dust, salty mist, rain, snow, hail, etc . . .) at the time. This has always made the maintenance and servicing of helicopters costly and burdensome.
Enclosing and thereby protecting such mechanisms is therefore very desirable. Preferably this should be accomplished without sacrificing weight, space and performance. Both cost and risks of part failure should not be increased but, if possible, even lowered. Also, such improvements should permit the use of a plurality of blades gyrating concentrically.